1. Field of the Invention
This invention relates generally to anaerobic treatment of wastes, and more particularly to an anaerobic migrating blanket reactor utilizing multiple compartments.
2. Description of the Related Art
The numbers in brackets refer to publications listed in the Appendix, the teachings of which are incorporated herein by reference.
Anaerobic treatment of industrial and domestic wastewater has proven to be sustainable over the last 20 years. Especially, the upflow anaerobic sludge blanket (ASB) process and its derivatives have shown good performances and stability in numerous full-scale operations world-wide 19, 20!. However, other immobilized biomass processes have been developed for several reasons. The loss of biomass with the effluent due to excessive bed expansion or poor granulation, for example, can pose problems to non-compartmentalized reactors like the UASB process 16!.
Compartmentalization in anaerobic reactors was first described by Bachman et al. 6! who developed the anaerobic baffled reactor (ABR). In this reactor, the wastewater flows under and over vertical baffles. Other compartmentalized reactor types have been developed like the horizontal-baffled anaerobic reactor 36!, the internal circulation (IC) reactor 17!, the multiplate anaerobic reactor (MPAR) 11!, the "biogas turmreaktor" 22!, and the upflow staged sludge bed (US SB) reactor 31!. An upwards feeding and reversing flow pattern has shown improved settling characteristics and granulation in the reversing anaerobic upflow system (RAUS). This system combines compartmentalization with a reversing flow pattern 8!. The two-stage anaerobic unitank system (TSU-AN-system), a modification of the UASB process, combines the same characteristics 9, 34!. In the above mentioned processes, an hydraulic upflow pattern is responsible for the contact between substrate and biomass. In addition to the compartmentalization, a difference between the ABR and the UASB process is the absence of a special gas-solids-separator system, which simplifies the design 7!. Moreover, the anaerobic sequencing batch reactor (ASBR) is a batch-fed process which does not have an hydraulic upflow pattern. This results in the absence of gas-solids-separator and feed-distribution systems 27, 2!. However, Wirtz and Dague 35! developed a granular blanket with an ASBR in five months after seeding the reactor with non-granular primary digester sludge. This result indicates that granulation does not solely depend on an hydraulic upflow pattern, which was also found by Vanderhaegen et al. 30!.
Those concerned with these and other problems recognize the need for an improved anaerobic migrating blanket reactor.